A knitted fabric is manufactured by knitting yarn by a knitting needle or a knitting stick, and it therefore has a texture in which a plurality of stitches are continuously intertwined with each other, and a high expansibility. In order to manufacture a knitted product, for example, a sweater etc. by sewing such knitted fabrics, a single-purpose sewing machine (which will hereinafter be referred to as "linking sewing machine") is used. As shown in FIG. 36, this linking sewing machine 80 is provided with a throat plate 82 on which a plurality of locking needles 81 are arranged at predetermined intervals similarly to the teeth of a comb.
Each of the locking needles 81 has a shape of the letter "L", and is provided with a locking portion 81a and a fixed portion 81b as shown in FIG. 37, the fixed portion 81b being fastened to a lower surface of the throat plate 82 by welding etc. The locking portion 81a is sharp edged at a free end section thereof, and provided with a guide groove 81c in a front surface thereof.
As shown in FIG. 38, loops (stitches) 83a of one knitted fabric 83 are fitted forcibly in order around the locking needles 81 on the throat plate 82 with loops 84a of the other knitted fabric 84 fitted forcibly in order therearound from the opposite side, a sewing needle 85 being then moved up and down to sew up the loops 83a, 84a of the two knitted fabrics together.
When the sewing needle 85 moves down from an upper dead center toward a lower dead center, a tip of the needle advances along the guide groove 81c of the locking needle 81 to pass between the loops 83a, 84a of the two knitted fabrics. The sewing needle 85 then enters a space under a sewing machine bed 86 through a hole 86a formed therein, and a sewing thread inserted through a thread hole of a tip portion of the sewing needle is guided to a position close to a tip portion 87a of a wedge-shaped looper 87. The looper 87, which is rotated in a predetermined direction, captures the sewing thread at its tip portion 87a when the sewing needle 85 enters into an upward return stroke, to form a loop, which is retained until the sewing needle 85 has thereafter moved down to the same position, the sewing thread being then passed through this loop to form a chain-like seam, whereby the sewing of the two knitted fabrics 83, 84 is attained.
The throat plate 82 is engaged with a table 88 of a comparatively large length disposed on the front side of the sewing machine bed 86 and extending so as to cross a sewing machine body at right angles thereto. A guide rail 89 is fixed (FIG. 37) to a lower surface of the throat plate 82, and fitted in a guide groove 88a formed in the table 88, so that the throat plate 82 is rendered laterally slidable on the table 88.
A feed gear 90 is provided below the throat plate 82, and meshed with the fixed portions 81b, which are arranged in the form of a rack on the lower surface of the throat plate 82, of the locking needles 81. This feed gear 90 is connected to a driving power source for the sewing needle 85 via transmission means, such as another gear 91 and a belt (not shown), and adapted to be rotated synchronously with the vertical movements of the sewing needle 85. Namely, each time the sewing needle 85 makes one upward and downward travel, the throat plate 82 slides by a distance corresponding to a distance between two adjacent fixed portions 81b, and a subsequent locking needle 81 moves to a position just under the sewing needle 85. The looper 87 is also connected to the above-mentioned driving power source via a transmission mechanism (not shown), and adapted to make one full turn synchronously with one upward and downward travel of the sewing needle 85.
Thus, the two knitted fabrics 83, 84 can be sewed together by forming a chain-like seam, so that a predetermined expansibility can be secured in the sewn portions of the knitted fabrics. Accordingly, the linking sewing machine can be adapted excellently to the property of knitted products having an expansibility. Since the sewing operation is carried out by carefully thrusting the locking needles 81 on the throat plate 82 into the loops 83a, 84a of the knitted fabrics, the loops are arranged beautifully on the sewn portion. This can not only improve the design effect but also effectively prevent the knitted fabrics from coming loose at terminal end portions thereof.
However, in order to beautifully arrange the stitch loops on the sewn portion as mentioned above, it is necessary that the locking needles 81 on the throat plate 82 be thrust into all the loops 83a, 84a in order without skipping any one of them, and this work is necessarily performed by manual operations of a skilled worker at present. Under the circumstances, even when the reduction of the sewing time is attempted by electrifying a driving means for the linking sewing machine 80, it takes time to set objects to be sewn on the throat plate 82, so that the improvement of an overall productivity by the sewing machine is greatly limited.
In a conventional linking sewing machine 80, it is necessary that a sewing machine body be replaced in accordance with the coarseness or density of the stitches of the knitted fabrics 83, 84, objects to be sewn. The coarseness or density of the knitted fabrics 83, 84 is determined by a gauge of the knitting machine, and the intervals of the locking needles 81 on the throat plate 82 are also regulated so as to match the same with the gauge. The timing of the upward and downward movements made by the sewing machine body of the sewing needle 85 and the intermittent feeding of the throat plate 82 is done fixedly in practice by selecting the kind and its combination of inside-provided gears. Therefore, in order to use a throat plate 82 matching the gauge of changed knitted fabrics 83, 84, the sewing machine body has to be replaced by a sewing machine body provided with a single-purpose gear structure specially adapted to this gauge, and this constitutes a large load on the improving of a labor effectiveness and a desire to make plant and equipment investment.
In order to obtain an article of clothing of certain function and design, the necessity of sewing a knitted fabric having a high expansibility and a woven fabric having a low expansibility together may arise. When the linking sewing machine 80 is used in such a case, stitches can be captured by the locking needles 81. This enables loops to be arranged on a sewn portion, and the characteristics of the knitted fabrics to be effectively utilized. However, when a woven fabric having a low expansibility is sewn so as to form a chain-sewn fabric having an expansibility, a lot of fine wrinkles occur on the woven fabric, so that using for this purpose a linking sewing machine made solely for knitted fabrics is not suitable.
Therefore, the sewing of a knitted fabric and a woven fabric together has heretofore been done by a lock stitch sewing machine which is used to sew woven fabrics together. Unlike a linking sewing machine in which fabrics are sewn together with one yarn to form a chain-sewn fabric, the lock stitch sewing machine is adapted to combine upper and lower yarn with each other, so that a rigid and non-expansible seam is formed.
When a lock stitch sewing machine is thus used, a dense and strong seam is certainly formed owing to the intertwined upper and lower yarn, and fine wrinkles do not therefore occur on the woven fabric. However, the lock stitch sewing machine does not, of course, have locking needles, and cannot sew knitted fabrics by carefully picking up the stitches thereof. Therefore, the loops of the knitted fabrics cannot be beautifully arranged, and they cannot be utilized effectively for the designing of the resultant sewn product. Moreover, there is the possibility that the yarn becomes loose at a terminal end portion of the sewn fabrics.
When a knitted fabric 83 and a woven fabric 92 are sewn together by conventional techniques by a lock stitch sewing machine as shown in FIG. 39, the lock stitch sewing operation is necessarily carried out with the portion of the knitted fabric 83 which is in the vicinity of a terminal end thereof put in a folded condition. Even when the terminal end portion of the fabrics thus sewn becomes loose, the loosened portion is stopped at a seam 93, so that the spoiling of an outer surface of the knitted fabric 83 can be prevented.
However, since the knitted fabric 83 which is thick by itself is folded, the thickness thereof increases twice, and the sewn portion is formed as if it were patchwork, this preventing the knitted fabric from being united naturally with the woven fabric 92. Consequently, the designs of articles of clothing are greatly restricted.
The present invention has been worked out with a view to solving these problems encountered in the conventional techniques of this kind, and aims at obtaining a means for sewing the stitches of knitted fabrics reliably even when these stitches are not set one by one accurately on locking needles, and arranging beautiful loops of stitches in good order on a sewn portion.
The present invention also aims at providing an ideal sewing means which enables one sewing machine body to deal with all types of stitches without replacing the sewing machine body by a single-purpose sewing machine body in accordance with the coarseness or density of the stitches of knitted fabrics.
The present invention further aims at providing a sewing means which does not have the possibility, even when a terminal end portion of a knitted fabric is not folded, that a knitted fabric and a woven fabric that are sewn together become loose, and which does not cause fine wrinkles to occur on the woven fabric.